Hydroxyapatite powder (HA) was coated with human whole saliva and injected subcutaneously into rabbits. The resulting antisera were reacted with commercial preparations of proteins by immunodiffusion and immuno-electrophoretic methods for tentative identification of antigens in the saliva coat on HA. Saliva proteins were eluted from the HA with phosphate buffer and reacted with specific antiserums using immunological techniques. Specific chemical and enzymic methods were also employed for identification of the coat proteins. IgA, IgA, albumin, lysozyme, a-amylase and bacterial glulcosyltransferase were identified as proteins present in the saliva coat on HA. Many, if not all, of these proteins could be involved in the colonization of oral bacteria.